[PATCH] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[PATCH] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Liu hua]

As sysctl_hung_task_timeout_sec is unsigned long, when this value is
larger then LONG_MAX, the function schedule_timeout_interruptible in
watchdog will return immediately without sleep :

for example (in x86_64 platform):

linux# echo 0xFFFFFFFFFFFFFFFF > /proc/sys/kernel/hung_task_timeout_secs

[   66.798350] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.800064] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.801774] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.803488] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.805225] schedule_timeout: wrong timeout value ffffffffffffff06

The screen was filled with "schedule_timeout: wrong timeout value
ffffffffffffff06" and the system stalled.

So I do some check and correction in timeout_jiffies, to let the function
schedule_timeout_interruptible allways get the valid parameter.

Signed-off-by: Liu Hua <sdu.liu@huawei.com>
---
 kernel/hung_task.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 06bb141..ef96650 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -186,7 +186,16 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 static unsigned long timeout_jiffies(unsigned long timeout)
 {
 	/* timeout of 0 will disable the watchdog */
-	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
+	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT)) {
+		pr_err("%s : wrong timeout value %lx\n",
+					__func__, timeout);
+		pr_err("Timeout value is set to MAX_SCHEDULE_TIMEOUT(%lx) now.\n",
+					MAX_SCHEDULE_TIMEOUT);
+		return MAX_SCHEDULE_TIMEOUT;
+	}
+
+	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
+			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
 }

 /*
-- 
1.8.5.5.dirty


.

Re: [PATCH] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Paul Gortmaker]

On 14-03-06 02:19 AM, Liu hua wrote:
> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
> larger then LONG_MAX, the function schedule_timeout_interruptible in
> watchdog will return immediately without sleep :
> 
> for example (in x86_64 platform):
> 
> linux# echo 0xFFFFFFFFFFFFFFFF > /proc/sys/kernel/hung_task_timeout_secs
> 
> [   66.798350] schedule_timeout: wrong timeout value ffffffffffffff06
> [   66.800064] schedule_timeout: wrong timeout value ffffffffffffff06
> [   66.801774] schedule_timeout: wrong timeout value ffffffffffffff06
> [   66.803488] schedule_timeout: wrong timeout value ffffffffffffff06
> [   66.805225] schedule_timeout: wrong timeout value ffffffffffffff06
> 
> The screen was filled with "schedule_timeout: wrong timeout value
> ffffffffffffff06" and the system stalled.
> 
> So I do some check and correction in timeout_jiffies, to let the function
> schedule_timeout_interruptible allways get the valid parameter.
> 
> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
> ---
>  kernel/hung_task.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 06bb141..ef96650 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -186,7 +186,16 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  static unsigned long timeout_jiffies(unsigned long timeout)
>  {
>  	/* timeout of 0 will disable the watchdog */
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You are breaking the above functionality/feature by declaring
zero invalid.

Paul.
--

> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT)) {
> +		pr_err("%s : wrong timeout value %lx\n",
> +					__func__, timeout);
> +		pr_err("Timeout value is set to MAX_SCHEDULE_TIMEOUT(%lx) now.\n",
> +					MAX_SCHEDULE_TIMEOUT);
> +		return MAX_SCHEDULE_TIMEOUT;
> +	}
> +
> +	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
> +			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>  }
> 
>  /*
> 

Re: [PATCH] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Liu hua]

on 2014/3/6 23:35, Paul Gortmaker wrote:
> On 14-03-06 02:19 AM, Liu hua wrote:
>> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
>> larger then LONG_MAX, the function schedule_timeout_interruptible in
>> watchdog will return immediately without sleep :
>>
>> for example (in x86_64 platform):
>>
>> linux# echo 0xFFFFFFFFFFFFFFFF > /proc/sys/kernel/hung_task_timeout_secs
>>
>> [   66.798350] schedule_timeout: wrong timeout value ffffffffffffff06
>> [   66.800064] schedule_timeout: wrong timeout value ffffffffffffff06
>> [   66.801774] schedule_timeout: wrong timeout value ffffffffffffff06
>> [   66.803488] schedule_timeout: wrong timeout value ffffffffffffff06
>> [   66.805225] schedule_timeout: wrong timeout value ffffffffffffff06
>>
>> The screen was filled with "schedule_timeout: wrong timeout value
>> ffffffffffffff06" and the system stalled.
>>
>> So I do some check and correction in timeout_jiffies, to let the function
>> schedule_timeout_interruptible allways get the valid parameter.
>>
>> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
>> ---
>>  kernel/hung_task.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
>> index 06bb141..ef96650 100644
>> --- a/kernel/hung_task.c
>> +++ b/kernel/hung_task.c
>> @@ -186,7 +186,16 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>>  static unsigned long timeout_jiffies(unsigned long timeout)
>>  {
>>  	/* timeout of 0 will disable the watchdog */
>         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> You are breaking the above functionality/feature by declaring
> zero invalid.
> 
> Paul.
> --
> 
Actually the patch will disable the watchdog if the timeout is illegal(except 0) for
schedule_timeout_interruptible.
I will make a new patch that disables the watchdog when the timeout is 0 or above
LONG_MAX without printing errors ?

What do you think?

Liu Hua
>> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT)) {
>> +		pr_err("%s : wrong timeout value %lx\n",
>> +					__func__, timeout);
>> +		pr_err("Timeout value is set to MAX_SCHEDULE_TIMEOUT(%lx) now.\n",
>> +					MAX_SCHEDULE_TIMEOUT);
>> +		return MAX_SCHEDULE_TIMEOUT;
>> +	}
>> +
>> +	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
>> +			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>>  }
>>
>>  /*
>>
> 
> .
>